What follows is an explanation covering some example markup that I've
done for Digg. This is a first cut and needs to be refined. It captures
some basic concepts on the site and shows how RDFa can be integrated
into Digg's existing HTML with relative ease. I made sure to not change
the existing structural layout - RDFa should be integrated into Digg
as-is, no major re-work necessary.
The validating XHTML file can be found here:
http://rdfa.digitalbazaar.com/demos/digg/stemcells.html
Here's the process that I went through when adding RDFa to Digg's page:
1. Set the DTD and HTML version to "XHTML+RDFa 1.0".
2. Cleaned up 94 validation errors on the page. The page now validates
cleanly as XHTML+RDFa 1.0 with minor changes to structural layout[1].
These pages can then be served to IE6/7 with minor changes to the
Apache configuration.
3. Read through a decent bit of the SIOC[2] (Semantically Interlinked
Online Communities) vocabulary to see what concepts it supported
and whether or not it mapped cleanly to Digg's site concepts.
4. Started adding SIOC to Digg's page using Fuzzbot[3] in Firefox 3 on
Debian Linux to debug the triples that were being generated. This
whole process made it clear that this advanced stage of editing
pre-existing sites is nearly impossible without proper debug tools.
I got to a point where, even though I know the RDFa processing rules
and have written a conforming parser for RDFa, I was not sure as to
what the output would be and resorted to trial-and-error at points -
depending on Fuzzbot to tell me which triples were actually being
generated. I was wrong about which triples I thought should be
emitted and which ones actually were emitted more often than I'd like
to admit.
Overall, the process took around 3 hours. The page uses a combination of
dcterms and sioc to express the following concepts:
* The Digg Community (sioc:Community)
* The various sections and sub-sections of Digg Politics, Technology,
Technology/Apple, etc. (sioc:Forum)
* Digg stories (sioc:Thread)
* Digg users (sioc:User)
* Digg replies (sioc:Post)
Various attributes for each of these concepts, such as avatar image,
relationship between posts and threads, who created each post and when
it was submitted, are also marked up. There will be follow-up e-mails
detailing each concept described above in more detail.
-- manu
[1]http://rdfa.digitalbazaar.com/demos/digg/stemcells.html
[2]http://sioc-project.org/ontology
[3]http://rdfa.digitalbazaar.com/fuzzbot/
--
Manu Sporny
President/CEO - Digital Bazaar, Inc.
blog: Bitmunk 3.0 Website Launches
http://blog.digitalbazaar.com/2008/07/03/bitmunk-3-website-launches